diff --git a/notebooks/additional_topics.ipynb b/notebooks/additional_topics.ipynb
index 392a3cf..e00787e 100644
--- a/notebooks/additional_topics.ipynb
+++ b/notebooks/additional_topics.ipynb
@@ -157,7 +157,7 @@
    "source": [
     "Note that if this is used on a time series that doesn't have a constant trend, any trend will be fit with the noise term and so there will be high predictive uncertainty in the forecast.\n",
     "\n",
-    "To use a trend besides these three built-in trend functions (piecewise linear, piecewise logistic growth, and flat), you can download the source code from github, modify the trend function as desired in a local branch, and then install that local version. This PR provides a good illustration of what must be done to implement a custom trend: https://github.com/facebook/prophet/pull/1466/files."
+    "To use a trend besides these three built-in trend functions (piecewise linear, piecewise logistic growth, and flat), you can download the source code from github, modify the trend function as desired in a local branch, and then install that local version. This PR provides a good illustration of what must be done to implement a custom trend (https://github.com/facebook/prophet/pull/1466/files), as does this one that implements a step function trend (https://github.com/facebook/prophet/pull/1794) and this one for a new trend in R (https://github.com/facebook/prophet/pull/1778)."
    ]
   },
   {
@@ -242,9 +242,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.8"
+   "version": "3.8.3"
   }
  },
  "nbformat": 4,
  "nbformat_minor": 2
-}
\ No newline at end of file
+}